The savory, earthy flavor of blue cheese on these crostinis pairs especially well with something sweet, although maple syrup here is a bit unexpected.
Make sure you use real maple syrup, not pancake syrup! Real maple syrup will give a more rounded flavor, where pancake syrup is just overly sweet sugar.
I prefer using a blue cheese with a lot of flavor, like a Danish blue, but just about any crumbly blue-veined cheese will work well here.